The Perth Agreement is an agreement made by the prime ministers of those sixteen countries of the Commonwealth of Nations which retain the Westminster model of constitutional monarchy ("the Commonwealth realms"). The document agreed to amend the succession to the British throne (and ancillary matters). The institutional and constitutional principles of Commonwealth realms are greatly and at root shared equally as enacted in 1931. The changes, in summary, comprised: replacing male-preference primogeniture ― under which males take precedence over females in the royal succession ― with absolute primogeniture (which does not distinguish sex as a succession criterion); ending disqualification of any person who had married Roman Catholics; and that only six people closest to the throne require t